1. Field of the Invention
The present invention relates to a cleaning blade, an image forming apparatus and a process cartridge.
2. Description of the Related Art
In electrophotographic image forming apparatuses, residual toner remaining on the surface of a photoreceptor even after a toner image thereon is transferred onto a recording material or an intermediate transfer medium is removed therefrom using a cleaner.
Strip-shaped cleaning blades made of an elastic material such as polyurethane rubbers are typically used for such a cleaner because of having advantages such that the cleaner has simplified structure and good cleanability. Among such cleaning blades, a cleaning blade in which one end thereof is supported by a supporter, and an edge of the other end is contacted with a surface of a photoreceptor to block and scrape off residual toner on the photoreceptor, thereby removing the residual toner from the surface of the photoreceptor.
In attempting to meet a recent need of forming high quality images, there are image forming apparatuses using spherical toner (hereinafter referred to as polymerization toner), which has a relatively small particle diameter and which is prepared by a method such as polymerization methods. Since such polymerization toner has such an advantage as to have higher transfer efficiency than pulverization toner, which has been conventionally used, the polymerization toner can meet the need. However, polymerization toner has such a drawback as not to be easily removed from a photoreceptor by a cleaning blade. This is because such polymerization toner has a spherical form and a small particle diameter, and easily passes through a small gap between the tip of a cleaning blade and the surface of a photoreceptor.
In attempting to prevent polymerization toner from passing through a gap between a cleaning blade and a photoreceptor, it is necessary to increase the pressure to the cleaning blade contacted with the surface of the photoreceptor to enhance the cleanability of the cleaning blade.
However, as disclosed in Japanese published unexamined application No. JP-2010-152295-A, when the contact pressure of the cleaning blade is increased, the friction between the cleaning blade and the photoreceptor is increased, and thereby the tip of the cleaning blade is pulled by the photoreceptor in the moving direction of the photoreceptor. Specifically, as illustrated in FIG. 8(a), a cleaning blade 62 is pulled by the surface of an photoreceptor 123 in a moving direction (indicated by an arrow) of the photoreceptor due to increase of friction between the blade and the photoreceptor, thereby causing a problem (hereinafter referred to as everted-tip problem) in that an edge line 62c of an apical surface 62a of the blade 62 is everted. In this regard, the thus everted tip has a restoring force, and therefore the tip tends to vibrate, resulting in generation of fluttering sounds. In addition, when the cleaning operation is continued while the edge line 62c of the cleaning blade 62 is everted, a portion of the apical surface 62a of the cleaning blade 62, which is apart from the edge line 62c by few micrometers, is abraded as illustrated in FIG. 8(b). When the cleaning blade 62 is further used for the cleaning operation, the portion of the apical surface 62a of the blade 62 is further abraded, resulting in lack of the edge line 62c of the blade 62 as illustrated in FIG. 8(c). The cleaning blade 62 having no edge line cannot remove residual toner from the surface of the photoreceptor 123, thereby forming an abnormal image in which background thereof is soiled with residual toner.
Japanese published unexamined application No. JP-2010-152295-A discloses a cleaning blade formed of a low-friction elastic blade, the edge line of which is impregnated with at least one of an isocyanate compound, a fluorine compound and a silicone compound; and a surface layer covering an edge line of the elastic blade, formed of a UV curing resin harder than the elastic blade.
The cleaning blade having an edge line a surface layer harder than the elastic blade is formed on can prevent the edge line from deforming in a travel direction of a photoreceptor. Further, even when the surface layer is worn out and an edge line of the elastic blade is exposed, the impregnated part thereof contacts the photoreceptor and a frictional force between the elastic blade and the photoreceptor is reduced to prevent the exposed part from deforming. This prevents the edge line from being everted and increases abrasion resistance of the cleaning blade to prevent poor cleaning.
Because of these reasons, a need exist for a cleaning blade preventing poor cleaning while having higher abrasion resistance than that disclosed in Japanese published unexamined application No. IP-2010-152295-A.